Imagery is the photographic or false-color material that has been acquired by means of remote sensing. The two most common types of remote sensing is air-born photography and satellite-based techniques. A very popular source of satellite imagery is the Landsat satellite series. Landsat imagery is available freely at the Global Land Cover Facility.

In order to assign the imagery its corresponding place on earth the image needs to contain geo-referencing information. Since that information is not part of a regular image format like PNG or TIFF, the geo-references are encapsulated by means of an extension of the TIFF format, the GeoTIFF format.

The most prominent library to read that format is the GDAL library via its libgeotiff sub-module. For more information about the supported GDAL image formats see here.